1. Field of the Invention
The present invention relates to a method of producing composite oxide ceramic and fluorine polymer layers on articles of aluminum, magnesium, titanium or their alloys, particularly of light metal components which are used in turbine driven pumps and in turbine technology. Also, the present invention relates to articles produced by the method.
2. Description of the Related Art
Components which rotate at high rates of rotation and which come into contact with corrosively acting media are made of metals which are either themselves chemically very resistant but expensive, or coating methods are used. For example, rotor and stator of turbine-driven molecular pumps which operate at rates of rotation of between 25,000 and 60,000 rpm are made of light metal alloys and are anodically oxidized in an aqueous electrolyte for protection against wear and corrosion due to gas/solid/liquid reactions. Rotors of molecular pumps which were provided with these protective layers and were used for pumping plasma-activated chlorine did have substantially longer service lives than rotors having other protective layers. However, these rotors did not meet fully the high demands made under the operating conditions of plasma-etching of aluminum or aluminum alloys with chlorine-containing gases which is conventionally used in the manufacture of micro-electronic components.
Light metals are frequently also used in aviation and space technology. In addition, magnesium and magnesium alloys have recently been used (Praxisforum 12/88: "Neue Werkstoffe und Oberflachenschichten bei Metallen und Polymeren in Entwicklung und Anwendung" [Development and Use of New Materials and Surface Coatings in Metals and Polymers]. N. Zeuner, G. Betz "Neue Magnesiumlegierungen fur die Luftfahrt- and Automobilindustrie") [New Magnesium Alloys for the Aviation and Automobile Industries.]
It is known in the art to manufacture oxide ceramic layers on barrier-layer forming metals or their alloys by a plasma-chemical anodic oxidation in aqueous organic electrolytes (P. Kurze; Dechema-Monographien Volume 121 -CH Verlagsgesellschaft 1990, pages 167 to 180 with additional literature references). The composition of such oxide ceramic layers is schematically illustrated in the reference. A thin tightly adhering barrier layer is provided on a metal, for example, aluminum. The barrier layer has a thickness of up to approximately 1 .mu.m and is very tightly connected to the metal. An oxide ceramic layer having few pores is sintered on the barrier layer. Because the molten oxide ceramic layer is quickly cooled by the electrolyte on the side toward the electrolyte, the gases which are still flowing away, particularly oxygen and water vapor, form an oxide ceramic layer having a wide-mesh linked capillary system. Examinations using electron scan microscopes determined pore diameters of 0.1 .mu.m to 30 .mu.m (CERAMIC COATINGS BY ANODIC SPARK DEPOSITION G. P. Wirtz et al., MATERIALS AND MANUFACTURING PROCESSES 6 (1), 87-115 (1991), particularly FIG. 12).
These known ceramic layers have thicknesses of at most 30 .mu.m which is insufficient when they are used as wear and corrosion protection layers.
By utilizing improvements of the method of the anodic oxidation with spark discharge which is the subject of a patent application filed concurrently herewith having the title "Method of Producing Oxides Ceramic Layers on Barrier Layer-Forming Metals", it is possible, inter alia, on aluminum, magnesium, titanium or their alloys to produce oxide ceramic layers which have substantially greater layer thicknesses of up to 150 .mu.m and are very abrasion resistant and corrosion resistant. This method disclosed in the above-mentioned application Ser. No. 07/982,092, filed Nov. 11, 1992, now U.S. Pat. No. 5,385,662 is expressly incorporated herein by reference.